1. Field of the Invention
The present invention relates to a torque sensor capable of detecting a torque by detecting the torsional angle of a torsion bar by the use of a pair of resolvers. It also relates to an electric steering device provided with such a torque sensor.
2. Discussion of the Related Art
As described for example in Japanese unexamined, published patent application No. 10-328952 (1998-328952), a resolver is provided on a servomotor and works to detect the rotational angle thereof. In recent years, there has been under development a torque sensor which is capable of detecting the torsional angle of a torsion bar provided inside a cylindrical body, in the form of electrical angles of a pair of resolvers different in the number of poles and which is capable of detecting a load torque corresponding to the torsional angle of the torsion bar, based on the difference between the electrical angles.
However, in the torque sensor of the aforementioned type, when the torsion bar is twisted beyond a predetermined angle, there arises a problem that the torque cannot be detected correctly because the difference between the electrical angles with the torsion bar twisted in a positive-going direction may become the same as that therebetween with the torsion bar twisted in a negative-going direction.
Further, in the aforementioned torque sensor, it is required to provide means for preventing the torsion bar from being twisted excessively, in which case it becomes a problem how to make such means downsized or miniaturized.